In a continuous casting machine, as shown in FIG. 1, molten steel 2 held in a tundish 1 is poured into a mold 3 by which the steel is cast into a slab S. The slab S is continuously withdrawn from the mold by a group of withdrawal guide rolls 5 (hereinafter called the guide rolls) onto a slab runout table 11 (hereinafter called the runout table). On the runout table 11, the continuously cast slab S is cut into desired lengths by a cutting device 12, and then forwarded to a subsequent process. This completes continuous casting operation. The length of the guide roll group 5 and that of a water-cooled zone 6 therein are appropriately chosen so that the central part of the cast slab S has solidified by the time it clears the delivery end of the guide roll group 5 or when it passes from the guide roll group 5 onto the runout table 11.
Conventionally, the cast slab S, after being cut by the cutting device 12, is cooled to room temperature for cold scarfing or temporary storage. Then it is reheated in a heating furnace and supplied to a subsequent rolling line. But cooling the cast slab S, which has a temperature as high as 1000.degree. C. or more at the time of completion of solidification, entails a great energy loss. In addition, the provision and maintenance of the cooling equipment, the heating furnace, etc. costs a considerable amount.
Recently, therefore, many attempts have been made to carry out so-called continuous rolling in a manner so as to supply continuous cast hot slabs directly to the rolling process, i.e. without carrying out the conventional cooling and reheating to the temperature required for the rolling operation for hot charging for supplying the cast slabs to the rolling process.
To permit such continuous casting and direct charging, it is essential to keep the slab temperature as high as possible by preventing the temperature from dropping during the travel of the slab through the continuous-casting machine. For this purpose, various heat escape blocking devices have been proposed.
However, a continuous casting machine comprises many pieces of equipment, instruments, etc. arranged in a small space. Moreover, a single machine can be changed over for casting slabs of different widths. Because of these limitations, the heat escape blocking devices thus far proposed have been nothing more than a casing substantially completely enclosing the guide rolls. Therefore, many problems arise, such as their practicality, the low heat blocking effect and various maintenance difficulties.